He is the Examiner of the Second Floor, as the Light Bearer position instructor.

Lero-Ro is fairly old, older than Yuri Zahard, whom he met when they were both Regulars. He and Quant are awkwardly described as a "Set Menu" by Yu Han Sung.

He is apparently quite famous, as his profile can be found on the network Light Bearers use. He took over 300 years to climb the Tower.

(Source: Tower of God Wiki)